answer: substrate concentration. enzymes work best when there is a high enough substrate concentration for the reaction they catalyse.
Answer from: Quest
when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.
Find and describe the climate zone in which you live, where else in the world do you find this climate zone? do you have any ideas about why the climates might be similar?